P0195: Engine Oil Temperature Sensor

P0195 means the engine control unit found an electrical fault in the engine oil temperature sensor circuit, so it can no longer trust what that sensor reports. It is a wiring and sensor fault, not a report that your oil is overheating. The usual causes are a worn-out sensor or a connector filled with oil, water or road salt. The car normally drives as before, but the oil temperature display, the oil service calculation and, on some diesels, the warm-up and injection maps all lose a value they use. Repair costs 45 to 150 euros where the sensor screws in from the outside. Where it sits inside the sump, as it does on BMW, VW Group and Mercedes engines, it is 135 to 420 euros, plus the oil and filter change that has to go with the job, so budget up to about 580 euros.

P0195 is a electrical-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0195 and illuminates the check engine light.

If your vehicle has triggered P0195, you may notice one or more of these symptoms:

• Check engine light on while the car still drives completely normally
• Oil temperature display reads cold, freezes at one number, or jumps around
• Oil level or oil service readout in the dash shows no value or an implausible one, on cars where the same sensor measures level
• Slightly rougher running in the first minutes after a cold start on some diesels, where the ECU has to work from a substitute oil temperature
• Cooling fan running at odd moments, but only on the engines that use oil temperature in their fan strategy, and normal fan cycling is not itself a fault

Here are the most common causes of P0195:

Generally yes, for short-term driving. Safe to drive in normal use. The oil is not actually too hot, the engine control unit has simply lost a reading it can trust, so there is no immediate mechanical risk. The catch is that you also lose the early warning that would tell you if the oil really did overheat, and on diesels the ECU falls back to a substitute value in its warm-up strategy. Fix it within a few weeks, and sooner if you tow or drive hard.

Follow these steps to pinpoint the root cause of P0195:

1. Read every stored code first and note whether P0195 arrived alone or alongside P0196, P0197 or P0198. Then read the freeze frame: a fault recorded on a cold start points at wiring, one recorded only when the engine was hot points at the sensor
2. Warm the engine fully and watch the live oil temperature value on a scan tool. A healthy engine settles somewhere around 90 to 110 C. A value pinned at the lowest or highest number the tool can display, or one that jumps around, is the fault you are chasing
3. Leave the car overnight, then compare oil temperature against coolant temperature and intake air temperature at key-on. On a cold engine all three should read within a few degrees of each other, so a large gap means the oil sensor is reporting nonsense
4. Find the sensor, which sits in the oil filter housing, the block or the underside of the sump depending on the engine, unplug it and look inside the connector for oil, water, green corrosion or spread pins. Clean and reseat it before condemning any parts
5. Test the circuit the way your sensor actually works, because most of the engines that set this code do not use a plain two-wire sensor. On a genuine two-wire thermistor, switch the ignition on and check for roughly 5 volts on one pin and a solid ground on the other, then unplug it and measure its resistance against the manufacturer figure for that temperature. On a BMW with the sump-mounted oil condition sensor there are three pins and nothing an ohmmeter can tell you: confirm the plug has battery voltage and a good ground, look at the single data wire with an oscilloscope, and check whether the alternator, the intelligent battery sensor, the glow module or the electric coolant pump have logged faults too, because they all share that BSD data line and one wiring fault can take several of them down together. On a VW Group G266 the three pins are battery voltage, ground and a pulse-width signal that runs to the instrument cluster, so check power and ground with a meter but read the actual value through the cluster with VCDS rather than probing for it. On Mercedes the sump sensor is pulse coded as well, so live data is the only meaningful test. Whichever type you have, wiggle the harness while watching the live value to catch an intermittent break
6. If sensor supply, ground and wiring all check out, fit an OEM or known-brand sensor, clear the code and drive one full warm-up cycle to confirm the reading tracks coolant temperature sensibly and the code stays away

Repair costs for P0195 vary depending on the root cause and your vehicle. Here are typical estimates:

P0195 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0195 or indicate related issues: